People often use the terms recommendation letter and reference letter interchangeably, but the two differ in both style and purpose:

A recommendation letter supports the candidate’s application for a specific scholarship, program, job or other opportunity.

A reference letter is a general endorsement of the person’s character, knowledge and skills.

Sending the Letter

In most cases, a letter of recommendation is sent directly to the university, employer or program director. You might never see the letter; some organizations request that it come from the writer and not from the applicant.
With a reference letter, however, the person writing it often gives it to the student or employee, allowing him to keep it on hand for future use.

Content and Structure

A recommendation letter is typically more specific than a reference letter. It addresses how well an applicant is qualified for a certain opportunity such as a fellowship or job. The writer not only comments on the person’s strengths and personal and professional qualities, but also elaborates on how his skills and talents make him the ideal candidate for the position. The writer might also expressly indicate that he recommends the person without reservation for the opportunity.
A letter of reference, on the other hand, is more general. The writer might discuss general characteristics such as the person’s work ethic, leadership potential or ability to work as part of a team.

Choosing the Right Person

When selecting someone to write a recommendation letter, choose a person who can comment on your qualifications for the specific position or honor. If you’re applying for an award or commendation, for example, ask your direct supervisor, who likely knows the quality of your work better than anyone.
You have more leeway when seeking reference letters. While you should never ask family, you can ask friends if you need a personal or character reference. You can also ask colleagues or people you know within the industry, in addition to or instead of your boss.

Etiquette

A recommendation letter usually comes with a deadline. Approach people well in advance – at least one month before you need the letter. If the organization asks that letter writers use an official form, fill in your name and other pertinent information. If the person will use his own letterhead, offer him a self-addressed, stamped envelope. Supply him not only with your resume and other information about your qualifications, but also with information about the program or job.
For a reference letter, ask two weeks in advance. Give the person information that elaborates on your qualifications or offer to write a draft letter he can use as a model.